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Table 11 **CIE L* a* b* colour parameters in Mg _x Cu _3-x V ₂ O ₈ (0 ≤ x ≤ 3) and Mg _y Cu _2-y V ₂ O ₇ (0 ≤ y ≤ 2) samples**

From: Structural characterization and colour of Mg_xCu_3-xV₂O₈ (0 ≤ x ≤ 3) and Mg_yCu_2-yV₂O₇ (0 ≤ y ≤ 2) compositions

x	Observed colour	Mg _x Cu _3-x V ₂ O ₈ samples fired at 600°C/12 h
		L*	a*	b*
0.00	dark brown	41.57	4.10	0.79
0.50	dark brown	43.59	5.83	6.82
1.00	orange	56.94	13.29	25.79
1.50	yellow	66.67	18.29	42.22
2.00	yellow	76.77	6.47	47.76
2.50	light brown	83.12	- 1.34	35.49
3.00	light yellow	94.76	- 2.00	13.35
y	Observed colour	Mg _y Cu _2-y V ₂ O ₇ samples fired at 600°C/12 h
		L*	a*	b*
0.00	dark brown	43.33	13.86	4.91
0.25	red-brown	38.34	20.54	9.80
0.50	red-brown	50.60	21.72	16.23
0.75	orange	46.88	25.71	29.13
1.00	orange	58.96	19.05	30.90
1.25	orange	57.06	19.77	46.16
1.50	brown	70.76	10.83	36.19
1.75	light brown	69.70	4.76	34.91
2.00	light yellow	92.46	- 1.35	22.95
x	Observed colour	Mg _x Cu _3-x V ₂ O ₈ samples fired at 800°C/1 h
		L*	a*	b*
1.00	dark brown	46.73	3.03	6.73
1.50	brown	53.37	4.77	15.20
2.00	yellow	68.97	12.02	41.84
2.50	light yellow	83.96	0.38	39.86
3.00	light yellow	95.50	- 3.57	11.54
y	Observed colour	Mg _y Cu _2-y V ₂ O ₇ samples fired at 800°C/1 h
		L*	a*	b*
0.50	dark brown	48.90	4.19	10.50
0.75	dark brown	47.58	3.95	8.75
1.00	brown	49.18	10.31	11.09
1.25	orange	52.11	13.11	16.37
1.50	orange	57.13	13.67	24.55
1.75	light brown	69.05	3.87	35.70
2.00	light brown	85.00	- 5.37	22.14
x	Observed colour	Mg _x Cu _3-x V ₂ O ₈ samples fired at 1000°C/1 h
		L*	a*	b*
1.00	grey	52.75	0.96	0.56
1.50	dark brown	48.74	1.15	4.58
2.00	dark brown	51.37	1.46	6.09
2.50	brown	58.02	2.69	12.51
3.00	yellow	94.28	- 4.86	17.95
y	Observed colour	Mg _y Cu _2-y V ₂ O ₇ samples fired at 1000°C/1 h
		L*	a*	b*
1.50	black	46.85	- 0.16	3.84
1.75	black-brown	47.39	0.31	3.86
2.00	yellow-brown	67.25	- 1.12	20.11

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